WITH PARTICULAR REFERENCE TO THE PHILOSOPHY OF SPINOZA
MARGARET GULLAN-WHUR
A^ Thesis Submitted for the Degree of Doctor of Philosophy in the Faculty of Arts, University of London
Department of Philosophy University College London
All rights reserved
INFORMATION TO ALL USERS
The quality of this reproduction is dependent upon the quality of the copy submitted.
In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed,
a note will indicate the deletion.
uest.
ProQuest 10045683
Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author.
All rights reserved.
This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC.
ProQuest LLC
789 East Eisenhower Parkway P.O. Box 1346
Spinoza's thesis of non-reductive monism was conceived in critical re'^pcnse to earlier
dualist and materialist theories of mind. He rejects dualism with respect to both
f jO 1-Nature and mind-body, yet his principles mark off the mental as severely as is
possible without forfeiting monism, showing his awareness that monism (attribute
identity) threatens mental irreducibility. The constraints Spinoza imposes in order to
preserve mental irreducibility and to make human beings partial expressions of one
thinking and extended substance produce a tension between mental autonomy and
mind-body identity. However, I propose that while this remains a serious
philosophical problem, some degree of tension must persist in any non-reductive monism which succeeds in giving the mental a weighting equal to the physical, and
that Spinoza's sensitivity to this requirement is instructive.
I argue, on the other hand, that Spinoza's theory of mind is irrevocably
damaged by his turning of the traditional Mind of God into the Mind of the Whole
of Nature in so far as he extrapolates from this Mind of God-or-Nature to finite
minds. In characterising finite minds as partial expressions of "God's" infinite
intellect I believe Spinoza becomes caught between his unorthodox conception of
God's Mind as all-inclusive and a retained conception of the Mind of God as all truths. I argue that by characterising our thoughts as fractions of the adequate and true ideas "in God", that is, by claiming them (i) to express in some measure
immediate judgement; (ii) to have a state of our body as a necessary feature of their
representational content, and (iii) to have a place in a determined, lawlike mental
concatenation, Spinoza creates a tension between two mental perspectives, namely a
metaphysical explanation of human mental states, and our ordinary mental
experiences. I argue that he fails acceptably to characterise the latter and that his
I am grateful to my supervisor, Mr Arnold Zuboff, for giving generously of his time
and interest, and for meticulous criticism of my use of Spinoza's texts. I would also
like to thank Dr Jerry Valberg for supervision at an early stage, and for his support
as post-graduate tutor.
I am greatly indebted to Professor Tom Sorell, without whose scholarly
criticism, suggestions and constant encouragement this thesis could not have been
completed.
I would also like to thank people who have kindly offered valuable
suggestions:- Mr Alan Hobbs, Dr Susan James, Dr Paul Noordhof, Dr Timothy
ABSTRACT p.2
ACKNOWLEDGEMENTS p.3
ADVICE REGARDING THE PRIMARY TEXTS p.6
INTRODUCTION p.7
CHAPTER 1 SPINOZA'S PRINCIPLE OF MONISM
(ATTRIBUTE IDENTITY) p.l4
§ 1.1 Early commitment: God and the mind are not outside Nature.
§ 1.2 The semi-formal arguments in Ethics for monism
regarding (i) God/Nature and (ii) attribute identity. p.l8
§ 1.3 Conditions for a principle of monism. p.25
CHAPTER 2 SPINOZA'S PRINCIPLE OF MENTAL AUTONOMY p.27
§ 2.1 Thought is not body, nor a property of body. p.27
§ 2.2 Thought is a natural property. p.32
§ 2.3 A proper tension between identity and autonomy. p.38
CHAPTER 3 SPINOZA'S PRINCIPLE OF MENTAL HOLISM p.41
§ 3.1 An infinite attribute of thought must contain all possible thoughts. p.41
§ 3.2 In one logical dimension an infinite intellect is all truths. p.49
§ 3.3 Minds which are parts of an infinite intellect know only in part. p.59
§ 3.4 Some mental events which threaten the holism principle. p.63
CHAPTER 4 SPINOZA'S PRINCIPLE OF MENTAL FORMAL BEING p.74
§ 4.1 Definitions and Formal Being. p.74
§ 4.2 All modes of thought are ideas. p.80
§ 4.3 All true ideas have formal being as units of knowledge,
immediate judgements. p.87
§ 4.4 Are inadequate ideas, having the same formal being as adequate
ideas, necessarily units of knowledge, immediate judgements? p.88
§ 5.1 Any idea has objective being. p.98
§ 5.2 A true idea is an objective essence. p.lOl
§ 5.3 The mind is the idea of the body: any human idea is the idea
of a state of an actually existing body. p.l04
§ 5.4 The face-value representational content of human ideas. p.l21
CHAPTER 6 SPINOZA'S PRINCIPLE OF INDEPENDENT MENTAL
CAUSAL POWER p.l28
§ 6.1 The gap in the evidence for 'parallelism'. p.l28
§ 6.2 There are (at least) two causal powers, each confined to its own
attribute. p.l43
§ 6.3 "So long as things are considered as modes of thinking, we must explain the order of the whole of Nature, or the connection of
causes, through the attribute of thought alone" (E2 P7 S). p.l49
§ 6.4 "The power of the mind is intelligence itself". p.l67
CONCLUSION p.l85
For full details of texts see Bibliography SPINOZA
Abbreviations
C Curley's translation of Ethics, Treatise on the Emendation o f the Intellect, Short Treatise on God, Man and his Well-Being, Principles o f Descartes's Philosophy, Appendix containing Metaphysical Thoughts and Letters 1-28.
E Ethics
TIE Treatise on the Emendation of the Intellect
KV Short Treatise on God, Man and his Well-Being
DPP Principles o f Descartes's Philosophy
CM Appendix containing Metaphysical Thoughts
TTP Theologico-Political Treatise
TP Political Treatise
P Proposition
D Definition
C Corollary
S Scholium
Exp. Explanation
L Lemma
Translation is Curley's (C) unless otherwise stated. Translation of Letters 29-84 is Wolfs. Translation of TTP and TP is Wemham's except for sections he does not translate, when it is from Elwes.
Double quotation marks are used for Spinoza quotations and technical terms.
"Nature" (or "God") is given a capital letter at all times to distinguish it from nature
(or essence).
"Emend" and "emendation" are retained as Spinozistic terms which involve his doctrine of logical interrelation (mental causality) between ideas.
"Sive, seu" Latin for 'or' denoting an identification of referent objects or an equivalence of terms. Such identifications and equivalences are indicated, after introducing them with textual evidence, by an oblique e.g. God/Nature.
DESCARTES Abbreviations
CSM I Rules for the Direction of the Mind, Discourse on the Method, Principles of Philosophy, Comments on a Certain Broadsheet, The Passions o f the Soul
CSM II Meditations, Objections and Replies
CSMK The Correspondence
I take the mind-body problem to be the philosophical question of what mind or 'the
mental' is, and how it is related to matter. This problem resists strategies designed
to resolve it since any solution advanced seems to generate intractable difficulties. At
one extreme the dualist, holding that mental substance is a distinct substance from
material substance, fails to explain how mind interacts with body since the two
substances have nothing in common. At the other, the reductive or eliminative
materialist, claiming that only truths about the brain make sentences about the mental
true, and that folk psychology is a primitive theory that deserves to be replaced by
neurophysiology, fails to allow for the scheme of mental explanation humans find
indispensable. Between these two polarities lie an array of non-reductive theories
of mind which do not posit distinct mental and material substances, but nonetheless
consider the mental irreducible to body. (I take 'mental irreducibility' to involve
some characterisation of the mental which logically prohibits the mental from being
subsequently redefined as physical and which affirms the mental as a reality in our
lives.) Non-reductive accounts are not uniform. For example, talk of mental
'properties' often indicates a commitment to some essentially or constitutively mental
feature, while reference to mental 'events' tends to signify a weaker claim about
diverse mental and physical meanings. But all such theories come up against serious
difficulties in attempting to supply a satisfactory account (that is, leaving no
unexplained or implausible entaiIments) of what it is about the mental that justifies a
claim of mental irreducibility, and how the mental and the material can constitute
radically different expressions of a single thing.
For Spinoza there is no mind-body problem. In his view, difficulties over
fixing the place of the mind in Nature are something earlier philosophers brought on
themselves. On the one hand, he says, they "did not observe the proper order of
philosophising" (E2 PIO 82), and on the other they "did not know the true nature of
to the general pattern of failure either preceding or following him. Spinoza stands
in many respects Janus-faced between Descartes and modem philosophy of mind, his
chosen framework of non-reductive monism being a popular current option, albeit
among people who do not associate it with Spinoza. While the interface of Spinoza's
doctrine with that of Descartes is intense, complex and instructive, his metaphysical
thesis, which stipulates an essential mental property and a system of independent
mental causal power, is thought-provoking for modern philosophers of mind in
showing what we may have to espouse if we take the project of mental irreducibility
seriously. I shall argue that far from presenting a model thesis of non-reductive
monism, Spinoza's theory of mind is ultimately unsatisfactory because in failing to
characterise all human thoughts it exposes a rift between how we experience and
explain our thoughts. Yet I suggest that his doctrine may take its prima facie
puzzling form just because he has foreseen certain difficulties which still beset
attempts to preserve mental irreducibility within a monistic framework, and that it
forces us to explore these issues thoroughly.
Six principles which govern Spinoza's theory of mind (or are premises
concerning a theorem of the mind-body relation) are addressed in turn below, in
Chapters named according to the principle under discussion. Spinoza does not
isolate these principles under the names I have given them but they are without
dispute principles of Spinozism, which Spinoza believes he has demonstrated.
Chapter 1 (Principle of monism or attribute identity) explicates Spinoza's
challenge to the Cartesian enterprise. In postulating autonomous attributes of mind
and body within one entity Spinoza rejects the notion of God's soul, and therefore all
soul, as inhering in a diverse entity from body (matter), so denying both Descartes's
dualism of God and the world and his dualism of the human mind and body. I argue
that Spinoza expresses his most fundamental objections to Cartesian principles in the
disguises the strength of his opposition to Descartes's substance dualism while
showing quite clearly the incoherences he perceives. I also make use of passages
from the early Short Treatise. This first Spinozistic text, written in Dutch for students, should not perhaps serve as sole evidence for claims about Spinoza's
doctrine, but it shows how central are some of its simply expressed notions to
Spinoza's later, more formal philosophy. I argue that in comparison to these early
texts Spinoza's semi-formal argument for monism or attribute identity at the start of
Ethics Part 1 lacks explanatory force. Nonetheless, I find in that argument two grounds for his belief in one substance, namely that no one attribute expresses the
whole of substance, since perfection/completeness requires all attributes, and that essential properties which have no effect on one another, but logically necessarily
complement each other because each requires the other for the expression of any
instantiation of God or Nature, must be identified in substance.
I do not question the label 'attribute identity' in relation to Spinoza's monism.
The identity theory in contemporary philosophy of mind allows that two diverse
properties may be united in one entity. Even so, in relation to a theory of mind
which espouses two essentially different properties this identity claim requires a brief explanation. Allison, to whose reading of Spinoza I am indebted, says
that:-'he [Spinoza] advocates a kind of mind-body identity theory, albeit a different one from the usual materialistic versions of such a theory in its insistence on giving equal weight to the mental' (Allison p.86).
Spinoza asserts more than once that mind and body are "the same thing" because they
are parts or modifications of attributes which are unified in substance. An attribute
characterises any state of substance, so any manifestation of substance exhibits this
identity: substance is always and everywhere both thinking and extended. Any claim
we make about a person is re-statable in terms of substance expressed in attributes.
A person is always both thinking and extended, in every aspect of his or her being.
Chapter 2 (Principle of mental autonomy) reflects Spinoza's antipathy to both
inhering in no further thing. But his thesis remains robustly metaphysical, and the
tension produced by the relation between diverse essential attributes within one entity
is still important. However, I suggest that this tension may be healthy. I conclude
Chapter 2 by demonstrating within a framework of dual aspect theory that theses of
non-reductive monism which do not exhibit a tension brought about by equal
weighting of the mental and physical are likely to fail to preserve mental irreducibility.
This discussion ends the part of my thesis concerned with the identity/
autonomy tension, apart from a review of it in the light of Spinoza’s principle of
independent mental causal power (§6.3). Discussion of the ensuing four principles
focuses increasingly on a different tension which I argue must be seen as fatally
damaging to Spinoza's theory of mind, namely that produced by Spinoza’s attempt to
extrapolate from the Whole-mind of God/Nature to the minds which are its fractional
expressions. Almost a century ago Harold H. Joachim objected that Spinoza’s
continuum of thought does not run seamlessly from infinite mind to finite minds
’It seems clear, then, that the world of presentation and ’natura naturata’ [Nature’s effects] as an order of distinct modes are in some sense 'facts’ which Spinoza has not brought into harmony with his general principles. And so far as his conception of the infinity of completeness is irreconcilable with the indefinite infinity of the finite - so far as there is a gulf fixed between the two forms of God’s causality - these 'facts’ appear for Spinoza under a form which comes into positive collision with these general principles’ (Joachim p.ll3).
It is my thesis that regarding several of Spinoza’s principles this view of Joachim’s is
in some measure tme. Joachim's complaint is put differently but with the same
general thrust in the 1930s critical commentaries of A.E. Taylor and H. Barker, and
with particular reference to the way in which an infinite mind and finite minds
represent external objects by Margaret D. Wilson (1980).
My interest in the key Spinozistic move from Whole-mind to part-mind has
been triggered by the interpretations of Allison (1975, revised 1987) and Genevieve
Lloyd (1994), which propose that if the mind is seen at each stage of interpretation
as "the idea of the body", then the move from Whole-mind to part-mind may be
organic complexity and, these commentators suggest, while this account of the mind-
body relation is full of obscurities and anomalies, it prompts a rethinking of various
issues still troubling philosophers. My stance on this falls midway between Barker's
and Taylor's scepticism and Allison's and Lloyd's (especially Lloyd's) charitable
interpretations. I have found (to a large extent as a result of Tom Sorell's stimulating
dissatisfaction with Spinoza's account of human thought) that we cannot save
Spinoza's doctrine from a conceptual chasm between what Spinoza thinks a mind must
be, and the specific content of our ideas. I have been helped in tracing the source
of this tension - which I find to lie in Spinoza's problematic conversion of the
traditionally perfect 'Mind of God' into the "perfect" (complete) Mind of the Whole
of Nature - by Edward Craig's The Mind of God and the Works o f Man, which places Spinoza's 'attempt to bring our minds as far as possible into congruence with the
divine mind' (Craig p.49) in its seventeenth-century context.
In each of the following Chapters I first explicate the relevant principle with
help from established commentators, showing how it is grounded in the all-inclusive
infinite intellect of God-Nature and in a retained traditional conception of the Mind of God as all truths or ideal mind, and also in what ways it is geared to preserving mental irreducibility. I then demonstrate the anomalies Spinoza creates for himself
in trying to give an account of human ideas based on that principle, and finally give
some indication of the bearing of his failure on the mind-body problem in general.
Chapter 3 (Principle of mental holism) examines Spinoza's claim that God's
Mind contains all partial or finite minds; shows how for Spinoza the infinite intellect
of God is in one logical dimension all truths, and suggests that if we are to agree on a definition of thought we must fix on a nature or essence shared by Whole-mind and
part-mind alike. (I use the general terms 'thought' and 'thoughts' throughout Chapters
1, 2 and 3, since argument is required to show that for Spinoza all thoughts are to be
defined as ideas, and this cannot be given due attention until Chapter 4.) The
discussion of Chapter 3 concludes, after considerable argument concerning Spinoza's
inference from what must be true of an infinite intellect which is all adequate and true
which anomalies such as evil and error are with difficulty - and some flexibility in
interpretation - included, that Spinoza's "infinite intellect" of God captures all possible
instances of thought, and that all, in being expressions of an infinite (self-contained
and all-inclusive) attribute, will share a basic nature or essence.
Chapter 4 (Principle of mental formal being) constitutes the first stage in
defining or fixing a Spinozistic mental essence. We encounter Spinoza's stricture
that the mental is exclusively "ideas", and that any idea is an immediate cognitive
judgement (affirmation or denial) because that is the formal being of "God's" ideas.
I argue that while this designation aptly characterises true ideas, and is plausibly
ascribed to more human ideas than might at first be supposed, Spinoza strains our
credibility in alleging that all human ideas have as their formal mental being a nature (albeit partial, fragmentary or confused) of instant cognitive judgement.
Chapter 5 (Principle of objective being) intensifies the lacuna between what
Spinoza thinks a mind must be, and the specific content of our ideas. On the one
hand, we see that God/Nature is all tme ideas of objects, and Spinoza's doctrine of the
identity of tme ideas with their objects supplies, in cases where those objects are particular bodies, a coherent thesis of mind-body pairs or unions. This doctrine does
not, as stated at this point, involve any thesis of causal ordering. Nor, considered
only as a tme correspondence of God's knowledge with objects which are internal to
God, does it address the question of representational content in the ideas of its parts
which, unlike the mind of Nature-whole, must represent objects which are external
to themselves. §5.3, on the other hand, constitutes a critical examination of Spinoza's
principle of objective being in the light of my claim that a different kind of objective
being is involved in the mere direction on the world of most human ideas from the
objective essence or identity relation proper to the agreement of idea with object
(ideatum) in the set of tmths of the mind of Nature-Whole. I argue that Spinoza's characterisation of the mental collapses because he insists that all human ideas
necessarily involve direct perception of the body. This is not tme in the case of all
examine the weaker Spinozistic claim that all ideas are necessarily intentional, that is,
they are necessarily 'of or 'about' something. I conclude that intentionality (objective
being) is not a necessary condition for any idea because there are human mental states
which do not represent anything outside themselves, but that Spinoza shows a special
grasp of the necessary conditions for intentionality to mark off the mental.
Chapter 6 (Principle of purely mental causal power) explicates what must be
intended by Spinoza as a clinching condition for mental irreducibility since it
postulates maximal mental causal efficacy and causal independence from the physical.
But this final principle concerning the theorem of the mind-body relation, expressed
in the 'parallelism' proposition of E2 P7 ("The order and connection of ideas is the
same as the order and connection of things"), requires exegetical help, since it seems
to me that Spinoza only justifies his claim of a nomic (lawlike) flow and inter
connection of mental events by relying on ancient assumptions about the logical mind
of God. In §6.2 I explicate the essentially diverse causal powers of extension and
thought in finite modes. In §6.3 I re-examine my claim that a degree of tension
between identity and autonomy principles may be necessary for the preservation of
mental irreducibility. I assess the explanatory profit and the implausibility of
Spinoza's dual causal flowchart involving an independent mental causal property by
relating this causal thesis to the modem doctrine of functionalism. In §6.4 I
scrutinise Spinoza's claim that all ideas are not only determined, so preventing free
decision, but that they are "the concern of logic" because the power of logical
reasoning can "emend" inadequate ideas in a way which reveals their logical
interconnections with adequate ideas. I propose that the destructive tension caused
by Spinoza's attempted inference from Whole-mind to part-mind undermines his
principle of independent mental causal power since there are human ideas which
cannot be shown to have a place in a lawlike scheme of mental inputs and outputs.
I conclude my thesis by briefly recapitulating the elements of Spinoza's theory
CHAPTER 1
PRINCIPLE OF MONISM OR ATTRIBUTE IDENTITY § 1.1 Early commitment: God and the mind are not outside Nature.
From the start of his philosophising Spinoza has three unswerving beliefs which conflict
with the Cartesian philosophy, namely that God cannot 'will' something that Nature does
not; that no mind, even God's, can be a separate substance existing outside Nature, and
that people must be unions of the same kinds of body and mind as is God. I suggest
that the reasoning behind these commitments is more revealingly stated in Spinoza's
early and political works than in the semi-formal argument for monism which occupies
the first fifteen propositions (together with related proofs, corollaries and scholia) of
Ethics Part 1, and to which we turn in the second section of this Chapter. The Ethics
argument is set within a paradigm of scholastic argument, and largely turns on premises
couched in terms of archaic principles.
While in the Cogita Metaphysica (Appendix to DPP) Spinoza tends to mask his
intense disapproval of Descartes's treatment of God, Nature and the human mind (or
soul), he nonetheless expresses grumbles which do not feature prominently in the initial
Ethics argument. As Meyer warns in the Preface (C p.230), Spinoza will address the implausible disparity Descartes allows between God's will, God's intellect and the laws
of Nature. Spinoza repudiates the Cartesian claim that although human beings are
created things their souls have an existence distinct from the body by God's divine
decree, that is, in apparent defiance of the laws of Nature. In Spinoza's view,
Descartes only establishes a human immaterial soul by incoherently pitting God's power
of acting against the laws of Nature which God himself has ordained, and which
Descartes gives us to believe are eternal and immutable tmths (Letter to Mersenne,
April 1630, CSMK p.23).^ In Ethics Spinoza does not argue until towards the end of Part 1 for the equation of will and intellect in God (yoluntate sive intellectu - E l P32
Cl), and not until towards the end of Part 2 that in humans "The will and the intellect are one and the same" (E2 P49 C). Yet the claim is in place in the earliest texts that
God cannot contradict himself by thinking or acting outside the laws of Nature.
Spinoza has already entered a philosophical minefield by arguing that, if God
is the 'most simple being' traditionally postulated, the objects of God's knowledge
cannot be a distinct substance from his God's
intellect:-"Outside God there is no object of our knowledge, but he himself is the object of his knowledge, or rather is his own knowledge. Those who think that the world is also the object of God's knowledge are far less discerning than those who would have a building, made by some distinguished architect, be considered the object of his knowledge. For the builder is forced to seek suitable material outside himself, but God sought no matter outside himself" (CM 2 vii, C p.327-8). "God is not composed of a coalition and union of substances" (CM 2 v, ibid. p.324), but "the whole natura naturata [Nature's effects] is only one being (CM 2 ix, ibid. p.333).
The clear conclusion to be drawn from the premises obliquely postulated in the
Appendix to DPP (CM) is that the soul is a natural phenomenon which does not exist
independently of God, but is a partial expression of God, or Nature.
Spinoza's Short Treatise, on the other hand, was secretly circulated to friends. In it he writes freely on the topic of "the soul"^ while requesting that due to "the
character of the age in which we live" the contents of the Treatise be communicated only very judiciously (KV 2 xxvi, C p.l50). The "character of the age" dictated, as
Descartes had also discovered, that religious orthodoxy was political correctness.
Spinoza claims openly to his friends that it is as incoherent to suppose that the human
mind could be a different substance from its body as it is to make God a "coalition" of
thinking and extended substances. God or Nature does not, as seen exist apart from
its 'body', but is united with all the objects of its thought in one entity
"Because of the unity which we see everywhere in Nature; if there were different beings in Nature, the one could not possibly unite with the other. .. From all that we have said so far it is clear that we maintain
that extension is an attribute of God. I.e. If there were different substances which were not related to a single being, then their union would be impossible, because we see clearly that they have absolutely nothing in common with one another -like thought and extension, of which we nevertheless consist" (KV 1, II §§17, 18 and Note e, C p.70).
We have here an early example of how Spinoza moves directly from the nature of the
relation of thought and extension in God to the mind-body relation in human beings.
It was Schopenhauer's view that 'Spinoza's philosophy consists mainly in the negation
of the double dualism between God and the World and between soul and body which
his teacher Descartes had set up' (The Fourfold Root of the Principle o f Sufficient Reason, quoted in Curley 1, p.l54). Denying the second dualism depends, for Spinoza, on denying the first. First then, we observe that if God's will or intellect cannot be outside Nature or subject to different laws, the human soul certainly cannot
be outside Nature or subject to non-natural laws. People are parts of the same
universal metaphysical system in which Nature and God act as
one:-"We do not ask, when we speak of the soul, what God can do, but only what follows from the laws of Nature" (CM 2 xii, C p.342).
For "man is a part of Nature, which must be coherent with the other parts" (CM 2, ix, C p.333).
These remarks, despite being somewhat veiled for Cartesian readers, signpost Spinoza's
thoroughgoing doctrine of determinism in Nature. However, his view that souls do
not have free will is brusquely asserted in the early Treatise on the Emendation o f the Intellect:- "As far as I know they [the ancients] never conceived the soul (as we do here) as acting according to certain laws, like a spiritual automaton" (TIE §85).
Given the tension Spinoza observes in Descartes's thesis between God's active
power and the laws of Nature, and his wish to resolve this tension, he must speak of
his single substance in terms of both God and Nature. Even had Spinoza never heard
of God before studying Cartesian philosophy he would have to take 'God's power' into
account when doing metaphysics in order to respond to Descartes's theory of mind.
While we may seem to be primarily or only concerned with a monism of mind and
On one reading of his motivation this is merely a question of placating orthodox
philosophers by fitting 'God' in as first causal principle, all omnipotence, omniscience,
and so on. Certainly Spinoza tries to push through an identification of the
traditionally acknowledged 'perfect' Mind of God with the "perfected" Mind of the
whole of Nature (perfectus also means complete) by, as we see shortly, a few arguments for attribute plenitude. However, it is my thesis that the God/Nature identity turns out
to be troublesome for Spinoza's theory of mind in ways he does not recognise, and to
an extent which undermines his theory of mind more decisively than his more
frequently criticised - and still contentious - thesis of mind-body identity.
By the time Spinoza comes to construct his argument for substance monism in
Ethics, he is openly committed to a God-Nature monism.^ He calls his single substance God; argues for this designation, and eventually supplies a formal
identification of God with Nature in the equation Deus, seu Natura (E4 Preface). I therefore refer henceforth to God/Nature when talking of Spinoza's one substance. This
way of referring to God has, I suggest, three useful functions. Firstly, while Spinoza
does not reduce God away, he clearly dispenses with the transient (external to Nature)
and purely immaterial creator-God worshipped in seventeenth-century Europe.
Regularly reminding ourselves through use of the term God/Nature that these epithets
are interchangeable may reduce the traditional religious gloss of Deus. Secondly, of all Spinoza's substance-equivalences"* I think the God/Nature best reflects his
metaphysical project of learning "the knowledge of the union that the mind has with the
whole of Nature" (TIE §13). Thirdly, the odd-looking conjunction signifies my
concern that the God/Nature monism constitutes the roots of what I argue is a major
tension in Spinoza's philosophy of mind.
^ At some point between excommunication (1656) and his third letter to the Christian secretary o f the Royal Society (1662) Spinoza crystallises this point, for says o f "this work o f mine which might somewhat offend the preachers - "I do not separate God from Nature as everybody known to me has done" (Letter 6).
§ 1.2 The semi-formal arguments in Ethics for monism regarding (i) God/Nature and (ii) attribute identity.
We have seen that the motivation for Spinoza's argument for just one substance is his
belief that it is incoherent to suppose that the divine mind of God (or any other mind,
therefore mind in general) exists outside Nature. Since Nature and God cannot be at
odds, they must be one, therefore all mind is both natural and, in a non-Cartesian
sense, "divine". However, in Ethics these relatively straightforward premises must be put in the formal terminology of Spinoza's day. He must supply convincing premises
for a claim (i) that God and Nature are identical and (ii) that thought and extension
constitute one, not two substances: that is, an essential attribute of thought is logically
necessarily an expression of the same substance (entity) of which the essential attribute
of extension (or any other attribute there could possibly be) is an expression - and that
this one substance must be God.
The Ethics argument for one substance, which is God, is a protracted and contentious area of Spinoza's philosophy and I do not supply a comprehensive
examination of it. I suggest that the generally acknowledged weakness of Spinoza's
premises here is due to a certain lacuna in expression between the almost
common-sense motivation for monism of the informal texts (quoted above) and the Proofs he
offers to defeat familiar and respected arguments and thereby convince professional
philosophers. For example, Spinoza must adhere to or explain why he redefines -technical terms such as substance and attribute, and he must involve well-established
arguments for the existence of God in order to justify in an acceptable way his belief
that God and one absolutely infinite substance are identical. I therefore forefront
those premises which support the commitments to monism I have already isolated in
Spinoza's earlier works.
Spinoza supplies an orthodox scholastic and Cartesian Definition of
substance:-"By substance I understand what is in itself and is conceived through itself, i.e. that whose concept does not require the concept of another thing, from which it must be formed" (El D3).
[Descartes's version: DPP 1, 51]).
From this point on, Spinoza's classification of substance and attribute diverges from the
Cartesian model. Firstly, Spinoza has a more austere view of substance than Descartes.
Whereas Descartes's doctrine of substance allows for created corporeal substances,
which exist 'by God's concurrence', and so depend on another (thinking) substance,
Spinoza argues that the mere independence of a substance (being self-conceived)
logically necessitates that it is self-produced (El P6 Proof), exists necessarily (El P7
Proof) or (by El D8) "eternally" i.e. as an eternal truth, and that it is "infinite"^.
Spinoza also uses the term attribute more strictly than Descartes. He concedes
that Descartes was the first to make thought and extension 'principal attributes', meaning
that they are not like Aristotelian propria, changeable qualities, states, or processes, but are defining properties, inmost or essential natures without which the thing cannot be
or be conceived. For Spinoza an attribute is an essential property, nor does he use the
word attribute to designate anything but an essential nature, whereas for Descartes there
can additionally be lesser, non-essential, Aristotelian-style attributes or qualities.
While Spinoza agrees that "By attribute I understand what the intellect perceives of
substance as constituting its essence"^ (El D4) he does not agree that an attribute
necessarily marks off a distinct substance. He must therefore persuade his
contemporaries (who, like his Amsterdam circle of friends, represented by de Vries in
Letter 8, at first assume a Cartesian framework of one attribute per substance), that a
single "absolutely infinite" substance (i.e. all there could possibly be in any possible
kind, and the only possible world) must express all attributes.
The attack on the Cartesian stipulation that there can be only one (principal)
attribute per substance, and that if we conceive an attribute we thereby posit a
^ "Infinite" means for Spinoza unlimited in its kind, including all that is logically possible - all possible expressions - in that kind (Letter 2, KV 1 ii 1 and E l P16 and Proof). A ll Spinozistic attributes are infinite whereas for Descartes mind is divine and infinite but extension, being created and no part o f the divine nature, is merely 'indefinite' (Principles 2, 21 and Letter to More, 1649 [CSMK p.364). For Spinoza an attribute which is "infinite" is unlimited in a wider sense than for Descartes, although Descartes defines God's infinity as 'that in which no limits of any kind can be found' (1st Replies to Meditations, CSM 11 p.81).
substance, starts with the stipulative Definition of E l D6^ and culminates in the
Scholium to E l PIO, where Spinoza claims that nothing bars an absolutely infinite
substance from expressing more than one attribute, although those attributes have (in
line with our perception of them) nothing in common. Spinoza seeks to undermine
the assertion of a difference of substance due to difference in "affection” (quality).
While we do perceive a difference between attributes because they have diverse natures, says Spinoza, and a substance is indeed distinguished by its attributes (El P5 Proof),
this does not mean either that the attributes actually denote different substances,® or
that attributes cannot belong to the same substance.
This notion is not original to Spinoza. The physician Regius had floated the
idea long before Spinoza began to philosophise. Descartes had responded to Regius
that 'that would be equivalent to saying that one and the same subject has two different
natures - a statement that implies a contradiction' ('Comments on Certain Broadsheet':
CSM 1 p.298). Spinoza insists that a substance may coherently be characterised by
an infinite number of essential properties without contradiction. He uses the familiar
notion of an essence to support his argument for monism:-"If something is absolutely
infinite, whatever expresses essence and involves no negation pertains to its essence"
(El D6 Exp.). - The essence of God/Nature is all possible essences. God/Nature is essence plenitude. And since for Spinoza an essence is equivalent to a nature or
attribute^, God/Nature is a single unified substance expressing all attributes. Spinoza
thus argues for a single absolutely infinite substance constituted by distinct essential or
constitutive properties which are, in being naturally and inextricably co-functioning, the
constituents of a unified whole. All attributes are united in the absolutely infinite
essence of God/Nature. That "essence", (that is, by E2 D2, what it cannot exist
’ "By God I understand a Being absolutely infinite, i.e. a substance consisting o f an infinity o f attributes, o f which each one expresses an eternal and infinite essence" (E l D6).
* Allison cites an ingenious response by Russell to the one attribute per substance dictum. He paraphrases Russell's argument:- 'Although we could certainly distinguish between the two Cartesian substances by referring to their distinct affections, we take this to mark a distinction between substances only because w e have already assumed that the distinct affections must belong to numerically distinct substances' (Allison p.54).
without, and how it is conceived or defined) is, while expressed in infinite independent
ways, single in being unified. It is unique in expressing all possible essences. And
since it is unique, an essence of substance would seem to be posited over and above the
essence of each attribute.
However, further argument seems needed to show that essence plenitude is not
a loose conjunction of natures but an identification of them, and it is sometimes thought
that Spinoza does not provide convincing evidence for this.^° That said, I believe
exegetical help on two fronts fosters the plausibility of Spinoza's claim. Firstly, it is
not often granted in the literature that although each Spinozistic attribute expresses the
whole of nature in one of its dimensions, all attributes are needed for God's reality or perfection, and therefore no one of them can express that whole nature." As Allison points out, Spinoza's retention of the definition of an attribute as "what the intellect
perceives" shows that he takes the notion of perspective and perception seriously
(Allison p.50). A thing would only be fully known in all its perspectives. This consideration seems to affirm that since only one aspect of Nature can be explained
through thought and one through extension, an explanation through one attribute is not
a complete account of substance. It is an explanation of Nature as Nature exists in one
dimension. Spinoza has shown in his earliest arguments that thought and extension
require one another, and are inseparable from one another. God is the necessary and
universal system of all possible facts, each of which has a thinking and an extended aspect.^^ While the attributes are infinite in their kind, they lack the absolute infinity
of the substance of which they are elements or constituents. Thus, while substance is
not an aggregate of attributes, it is a union of complementary properties, no one of
This claim has been made, notably by Gueroult, who claims Spinoza has no monism because no 'absolutely infinite' essence is shown to exist over and above the irreducible infinite-in-kind essences o f each attribute (Gueroult 1 p.238). Gueroult holds that Spinoza's arguments posit instead a self-produced plurality o f substances, each infinite in its kind and expressing a single attribute entirely and uniquely (ibid. p .l41). A detailed defence o f Spinoza's claim versus Gueroult's based on Spinoza's revolutionary claim about God is found in Donagan (1). Donagan also offers a different defence, which I introduce below (p. 19).
" This point is owed to Barker (Barker 11 p. 124) and Curley (Curley 1 p. 16).
which expresses the absolutely infinite essence of substance, and each of which requires
the other for completion. A further argument supporting this identity premise, based
on the agreement of true ideas with their objects, is given in §5.3 below.
The other exegetical help comes from Donagan, and - paradoxically yet usefully
for Spinoza's assertion of mental irreducibility - makes monism depend on the diverse and essentially distinct natures of the attributes. As Allison observes, although
Spinoza's thesis is a monism, 'the very formulation of this thesis involves a dualism of
sorts' (Allison p.63). Statements of attribute independence are made in the E l
Definitions, and appear in Propositions 5, 6 and 9, that is, in the heart of the argument
for monism. (It is not surprising that Cartesians were confused by Spinoza's arguments
for monism, since he retained part of their central argument for dualism while denying
that it had any force to entail dualism!) Donagan assists Spinoza's intentions by
pointing out that his claim is not best expressed by the words "although attributes may be conceived as really distinct .. we still cannot infer from that that they constitute two
beings, or two different substances" (El PIO S - my emphasis) but by stressing that
because they are conceived as entirely different - having nothing in common - they
cannot exclude one another from the same substance (Donagan 2 pp.72-3 and 79-80). They have no power to do so because "a body is not limited by a thought nor a thought
by a body" (El D2). This stronger expression of the non-prevention claim gives
Spinoza what he needs with respect to both monism and non-reduction. It also shows
(I propose) why he will not be espousing a doctrine of mind-body interaction. Quite
simply, the attributes have no causal clout regarding one another. That they cannot
"limit" one another does not just mean that one cannot stop the other being necessary
or eternal, but that the power of one has absolutely no effect on the other. ('Like a
knife on air' may give the right impression, although of course a knife does have a
physical effect on air.) On this view, establishing monism entails repudiating attribute
interaction, so this premise has the merit of cohering with the other principles Spinoza
advances with regard to mental irreducibility and the union of the mind with Nature.
whole of substance since perfection/completeness requires all attributes, and that essential properties having no causal effect on one another, but complementing one
another in a logically necessary fashion because each requires the other for the
expression of any instantiation of God/Nature, must be identified in substance.
Finally, we should note how Spinoza formally demonstrates his earliest
conviction that God cannot be outside any substance by establishing that the one
substance, constituted by all possible essences, must be identical with God.
First, he exploits the scholastic argument for "God's perfection" to try to show
that only God can match up to our concept of substance. We have seen that he uses
perfectus in its nonevaluative sense of 'perfected' or complete (or maximally real
-realitas sive perfectio [E2 PI S]), a shrewd recasting of the divine mind as complete mind on Spinoza's part, since in due course he will have to show how "Whatever is, is
in God [Nature], and nothing can or be conceived without God [Nature]" (El P15). His
argument is sparse (El P9), and relies on an equation of perfection with reality (E2 PI
S) and reality with the Being of Substance (El PIO S). Spinoza can count here, as
Lloyd notes, on the assumption of his contemporaries that whatever we postulate as a
most real or perfect (complete) being must contain all possible attributes or it would
lack something. Conversely, as he has argued in the Short Treatise, the more attributes we conceive a thing to have, the more reality it necessarily has. Spinoza
reiterates this in E l P ll S to persuade his Cartesian readers that an absolutely infinite
substance must contain all infinities, and that such a maximally real and complete being
must be God, and must
exist:-"Perfection, therefore, does not take away the existence of a thing, but on the contrary asserts it. But imperfection takes it away. So there is nothing of whose existence we can be more certain than we are of the existence of an absolutely infinite, or [sive] perfect Being, i.e. God."
While this argument looks weak to us, it was would be hard for a Cartesian to deny that
'God' must be the 'most real being', given that one must be conceived to exist. We
know Spinoza was on non-Cartesian grounds convinced at a very early stage that God,
All"):-"The reason for this is that since Nothing can have no attributes, the All must have all attributes; and just as Nothing has no attributes because it is nothing, Something has attributes because it is something. Consequently, God, being most perfect, infinite, and the Something- that-is-all, must also have infinite, perfect, and all attributes" (KV 1 ii. Note a, C p.65).
Secondly, Spinoza exploits the scholastic assumption that there must be a cause,
or reason, for the existence or non-existence of any thing, and the self-evident truth
denying that a thing can have for its cause something other than what has already been
postulated as Supreme Being, sole cause of itself and sole causal principle (El P ll
Proof). This claim will be given extensive attention later, in Chapter 6, when the
distinct metaphysical principle of causation is discussed. Spinoza describes this Proof
as an a posteriori proof of God's existence from his effects. In my view it only
indirectly addresses Spinoza's prime concern that God cannot be in conflict with the
laws of Nature, and that the reason or cause of a thing's existence is immanent in God,
who, as Spinoza will spend much time later in Ethics Part 1 explaining, does not wield capricious power "like the power of Kings" (E2 P3 S). What Spinoza is really intent
to drive home - although he does not dwell on this point in the earliest Propositions of
Ethics, but a little later on - is the absurdity of supposing God can cause things by inconsistently 'willing' rather than by the necessity of his own
nature:-"From the necessity of the divine nature alone, or (what is the same thing) from the laws of his nature alone, absolutely infinite things follow" (El P17). "Others think that God is a free cause because he can (so they think) bring it about that the things which we have said follow from his nature (i.e. which are in his power) do not happen or are not produced by him. But this is the same as if they were to say that God can bring it about that it would not follow from the nature of a triangle that its three angles are equal to two right angles; or that from a given cause the effect would follow - which is absurd" (El P17 SI).
Spinoza devotes the second half of Ethics Part 1 to the notion that God must be an immanent cause, internal to Nature, and an efficient cause in so far as 'he' is not a final
cause (i.e. causing things to happen for some purpose). Spinoza does not make God
Cartesian sense that God controls things from outside Nature.
We now assume, as Spinoza does, that the God/Nature identity is in place, and
reflect on what he has established regarding the monism of mind (thought) and body
(extension) which would seem to be the dominant monism associated with the term
'non-reductive monism'.
§ 1.3 Conditions for a principle of monism.
In my view, the two premises for monism we isolated in Spinoza's early Ethics
argument demonstrate Spinoza's awareness that monism may be a threat to mental
irreducibility; that is, that a thesis of non-reductive monism which does not ensure that
the mental is given a weighting equal to that of the physical may collapse into
materialism. It is likely that this awareness arose from contemplating Hobbes's
materialist thesis, which was widely disseminated and discussed throughout the period
of Spinoza's philosophising. Since Spinoza never directly addresses Hobbes's claim,
my argument is based on inferring from what we know Spinoza studied to what he
postulates. Oldenburg echoes contemporary disquiet among philosophers and
scientists about the Hobbesian thesis when he asks Spinoza
'Are you certain that body is not limited by thought, nor thought by body? For the controversy about what thought is, whether it is a corporeal motion or some spiritual act, entirely different from the corporeal, is still unresolved' (Letter 3).
Spinoza must have also felt the impact of Hobbes's attack (in his Objections to
Meditations, which we shortly discuss further) on Descartes's certainty that his awareness of himself could not, in fact, have been caused by his own corporeal nature.
Spinoza must have seen that if Descartes's postulation of an independent thinking
substance was deemed insufficient to show that the mental is not caused or limited by body, then a stout metaphysical thesis claiming two essential properties from the outset
was required. It seems Spinoza foresees that if we are working within a framework
of non-reductive monism, that is, within parameters where there is a fundamental commitment to preserving mental irreducibility, then our stated conditions for monism
physical, nor make a thesis of monism implausible. Cynthia Macdonald has made an
intensive study of assumptions and principles governing identity claims. She points
out that if an argument for an identity theory is to be non-trivial, initial assumptions
must not either foreclose its possible tmth (i.e. make it impossible for the mental to be
identical with the physical following any amount of argument) or anticipate identity by
working with conceptions of the physical and the mental that are logically dependent
on one another (Macdonald pp.4-5).^^
It is not possible to say in advance of explication of the attribute autonomy
principle and of the defining characteristics of the attributes of thought and extension
whether Spinoza's properties, which are logically bound together and necessitate each
other, are also 'logically dependent' on one another. However, if some criticism of
Spinoza's identity principle is to be made now on the grounds of Macdonald's stricture,
then I think he must err on the side of logical mrerdependency of thought and extension on one another, rather on the side of than radical preclusion of identity, simply on the
basis that we have to think harder about the issue of logical independence and defer our
conclusion on it. On the other hand, I argue in Chapter 2 that any more stringent
conditions than Spinoza offers for attribute autonomy would put monism out of the
question. While Macdonald's strictures enable us to look critically at what is going
on in the hidden assumptions and motivations which underlie theses of non-reductive
monism, and allow us in some cases to expose obvious prejudgement of the issue of
identity (e.g. in physicalist theses where the mental is defined as a secondary physical
property), Spinoza preserves what I shall argue (after the principle of mental autonomy
has been expounded, at the end of the following Chapter) is a healthy tension between
identity and autonomy, granting both and denying neither.
CHAPTER 2
PRINCIPLE OF MENTAL AUTONOMY
§ 2.1 Thought is not body, nor a property of body.
In this first section of Chapter 2 I demonstrate Spinoza's awareness that materialism is
wrong. In §2.2 I show his rejection of immaterial substance. In §2.3 I argue that the
tension Spinoza maintains between his identity and autonomy principles is defensible.
While Spinoza's move in making God "immanent" (El P18) in Nature was
regarded as heretical by all orthodox Judaeo-Christian authorities, his claim that all
thought must be entirely natural was equally scandalous, and was sometimes mistaken
for materialism^ (or physicalism: I do not distinguish these terms). Materialism was
familiar enough to Spinoza for him to reject it firmly in his first
text:-".. it is necessary that what [man] has of thought, and what we call the soul, is a mode of that attribute we call thought, without any thing other than this mode belonging to his essence ... Similarly, what he has of extension, which we call the body, is nothing but a mode of the other attribute we call extension" (KV Appendix 11, 1-2).
Spinoza was aware of Hobbes's belief that thought consisted solely in body motions.
For Hobbes, there is only corporeal substance: body and substance are two names for
the same thing, "For the universe, being the aggregate of bodies, there is no real part
thereof that is not also body" (Hobbes 1, 3, 34, p.428). 'Incorporeal substance' is a
contradiction in terms (ibid. p.429). 'Mind' is body; so is spirit, which is air, vital and
animal spirits, 'subtile, fluid, and invisible body' (ibid. pp.429, 440). Hobbes tells
Descartes that it cannot be inferred from experience that the soul is purely thought
'It does not seem to be a valid argument to say, "I am thinking, therefore I am thought", or "I am using my intellect, hence I am an intellect'" (2nd Objection, 3rd Replies to Meditations y CSM 11 p. 122).
On the contrary
'... it may well be the case' [that] 'mind will be nothing but the motions in certain parts of an organic body' (ibid. p.l26).
Hobbes's materialist view was that attacked by Cudworth (1678) as the falsehood
'that Cognition, Intellection and Volition are themselves really nothing else but Local
Motion or Mechanism, in the inward parts of the brain and heart' (Yolton p.7). But
it is not Spinoza's view, and was not so considered in his day by those who understood
his doctrine. Philosophers who lived soon after him, including Bayle and Hume,
called him an atheist on the grounds that his God was extended, not above or beyond
the natural world and having no 'personality'.^ Hume recognises that Spinoza's
'hideous hypothesis' is of 'two different systems of beings presented', one of which
(although both are included in the same substance) is non-material (Treatise Bk.l Pt.lV §V). Spinoza was rarely accused of making God or soul merely matter. His 'two different systems' of matter and mind, existing in God the One Substance, were amply
recognised and reviled. Leibniz refers to the 'error of Materialists and o f Spinoza' of not allowing God's power to go infinitely beyond his creation (Leibniz 1 p.209, my
emphasis.) Like Hobbes, Spinoza holds that there is only Nature. But Nature is not,
as Hobbes believes, only body.
While Spinoza opposes Descartes by making the attributes inhere in one
substance, we have seen that his commitment to the irreducibility of the mental makes
him retain part of a Cartesian principle in fixing an attribute as an essential property,
saying that an attribute is "what the intellect perceives"; and claiming that, like a
substance, an attribute involves the concept of no other thing (El D4).^ Spinoza makes
the additional Cartesian claim that we perceive the mental as an independent essence
because it is independent. While he does not think that whatever we conceive as
logically independent of another thing is also an ontologically independent entity or
substance, he does hold that whatever is conceived as distinct is essentially distinct
"Things that have nothing in common with one another also cannot be
^ See Letter 12A on this, referring to KV 2 viii, which Meyer begged Spinoza to alter before publishing his Principles o f Descartes's Philosophy). Bayle makes a logical objection to God considered as extended, claiming that if God is mutable and divisible, then modes are His parts and are separate substances (Bayle p.308). He does not accuse Spinoza of materialism.
understood through one another, or the concept of the one does not involve the concept of the other" (El A5).
In the same way, we do not reduce body to a phenomenal experience. That which we
perceive to be body really exists as body, in
itself:-" .. man consists of a mind and a body, and the human body exists, as we are aware of it" (E2 P13 C).
Spinoza believes reality is known in its most general properties, and in the deductions
we can make from these, and he resists the idea that the attributes are limited to man's
"fictions" (KV 1 i Note d, C p.63). His admission that there may be an infinity of
attributes/natures/essences we do not know (ibid.) has no force if we do not accept that
"So far, however, only two of all these infinite attributes are known to us through their essence: Thought and extension" (KV 1 vii Note a, C p.88)."
The two attributes of thought and extension are essentially distinct, and distinctly
known. While Spinoza's assertion that "all the distinctions we make between the
attributes of God are only distinctions of reason - the attributes are not really
distinguished from one another" (CM 2 v) has been taken, together with his stricture
that an attribute is "what the intellect perceives", to suggest that Spinoza has a
subjectivist view of the attributes (i.e. they are ways a single thing appears to us, and
are not really different from one another), it is now generally considered that this
reading is unreliable.^ For example, when Spinoza refers to an attribute's being
"really distinguished" he is saying that the attributes are not 'really distinct' in a
Cartesian sense; that is, they are not distinct substances. And when he uses the
scholastic term "what the intellect perceives" he does so for the express purpose of
marking off the mental as conceptually and explanatorily distinct from the physical.
making direct appeal to his readers' belief that the attributes appear different because
they are different. Far from making the attributes merely conceptually distinct, or
distinctly observed phenomena, Spinoza adds constraints on causality and explanation
which estrange the mental from the physical more radically than does Descartes's
doctrine of diverse substances. For Spinoza, only the mental can explain the mental
because only the mental can cause the mental. (Much more is said on this.) For Descartes this is not the case. Some acts of thought (e.g. sensory perceptions and
passions) are for Descartes closely connected with the laws of motion and rest, and so
appear to be causally dependent on body. They do not consist in thought alone, and
'must not be referred either to the mind alone or body alone. These arise ... from the close and intimate union of our mind with the body'
(Principles 1 §48 CSM 1 p.209). '... the passions are to be numbered among the perceptions which the close alliance between the soul and body renders obscure and confused' (Passions §28, CSM 1 p.339).
Descartes's stated thesis of interaction is that the 'actions of the soul' involved in making
judgements interact with brain activities in the pineal gland (Passions 31-2). The Cartesian mind 'applies itself to corporeal motions [5th Replies to Meditations §4]), and disturbances in the body can 'prevent the soul from having full control over its passions'
(Passions 1,46). For Spinoza, the mental, that is, all possible "modes or ways of being of the attribute of thought, constitutes a holistic system, a realm of purely mental
activity and explanation. Conversely, since no other attribute shares the mental causal
system, the modes of no other attribute can be explained through thought
"Each attribute is conceived through itself without any other. So the modes of each attribute involve the concept of their own attribute, but not of another one; and so they have God for their cause only insofar as he [it] is considered under the attribute of which they are modes, and not insofar as he [it] is considered under any other, q.e.d." (E2 P6 Proof). "The body cannot determine the mind to thinking, and the mind cannot determine the body to motion" (E3 P2).
